Thin film resistor printhead architecture for thermal ink jet pens

Abstract

A thermal ink jet printhead including a thin film substrate with a plurality of polygon shaped thin film resistors, a barrier layer overlying the substrate, and respective firing chambers formed in the barrier layer for each of the resistors. Each firing chamber is formed of a continuously curved concave wall having ends adjacent the boundary of the resistor, and which is within the boundary of the area defined by the resistor and a 10 micrometer wide margin around the resistor.

What is claimed is: 
     
       1. A thermal ink jet printhead comprising: a thin film substrate with a plurality of thin film resistors each substantially polygon shaped in plan view;   a barrier layer overlying the substrate; and   respective firing chambers formed in said barrier layer for each of the resistors;   each firing chamber formed by a continuously arcuate concave barrier wall that is within the boundary of an area defined by the resistor and a 10 micrometer margin around the resistor, said barrier wall having ends adjacent the perimeter of the associated resistor and forming a single opening into said firing chamber.   
     
     
       2. The thermal ink jet printhead of claim 1 wherein portions of said barrier wall are inside of the perimeter of the associated resistor. 
     
     
       3. The thermal ink jet printhead of claim 1 wherein portions of said barrier wall are outside of the perimeter of the associated resistor. 
     
     
       4. The thermal ink jet printhead of claim 1 wherein each of said resistors is square, and wherein each of said firing chambers is formed of a barrier wall that is a partial circular cylinder. 
     
     
       5. The thermal ink jet printhead of claim 4 wherein said barrier wall passes on the inside of the vertexes of the associated resistor. 
     
     
       6. The thermal ink jet printhead of claim 1 wherein each of said resistors is rectangular, and wherein each of said firing chambers is formed of a wall that is a partial elliptical cylinder. 
     
     
       7. The thermal ink jet printhead of claim 6 wherein said barrier wall passes on the inside of the vertexes of the associated resistor. 
     
     
       8. A thermal ink jet printhead comprising: a thin film substrate with a plurality of thin film resistors each substantially square shaped in plan view and each having a side dimension L;   a barrier layer overlying the substrate; and   respective firing chambers formed in said barrier layer for each of the resistors;   each firing chamber formed of a partial circular cylinder barrier wall having a cylinder axis that passes through the center of the square shape of the associated resistor and a diameter that is less than L+20 micrometers, said barrier wall having ends adjacent the perimeter of the associated resistor and forming a single opening into said firing chamber.   
     
     
       9. The thermal ink jet printhead of the claim 8 wherein said cylinder diameter is greater than the resistor side dimension L and less than L+20 micrometers. 
     
     
       10. The thermal ink jet printhead of the claim 8 wherein said cylinder diameter is substantially equal to the resistor side dimension L.